How is a bone marrow performed?

Typically, only a local anesthetic is required to numb the skin and tissue down to the surface of the bone. A small cut (less than one-quarter inch) is then made in the skin. A hollow needle whose center is filled by a removable metal rod called a trochar is used to penetrate through the dense outer shell of bone. Once inside the bone, the trochar is removed and a syringe is attached to the now hollow tube of the bone marrow needle. The bone marrow is withdrawn as a thick liquid by pulling back on the plunger of the syringe and collecting the liquid. This sample is known as the marrow aspirate. This part of the procedure only lasts a few seconds, but is usually the most painful due to the sudden sense of a negative pressure inside the bone.

A biopsy can also then be obtained in addition to the marrow aspirate or when an aspirate cannot be obtained. The same needle is used but without the center portion in place. As the needle is partially rotated into the bone it cuts a core which is trapped inside the needle. Once the needle is removed, this core can be extracted from the needle barrel. This core can then be prepared with fixatives and stains for examination under a microscope.

Since the skin cut for a bone marrow procedure is usually very small, no stitches are generally necessary and only a bandage is applied.

What is done with the bone marrow sample?

The bone marrow core biopsy is first placed in a liquid that keeps the cells in their natural condition (fixative solution). The sample is then placed in a solution to soften the bone and is finally processed like other biopsies in the tissue study (histology) laboratory. The liquid portion of the bone marrow is spread on glass slides and stained to make the bone marrow smears. The slides are then examined under the microscope, usually by a specially qualified technician or physician such as a hematologist or pathologist.

Portions of either sample may be submitted to the microbiology laboratory for cultures. Certain conditions may require other specialized studies such as genetic testing or cell marker studies.